import java.util.Scanner;

public class 跳台阶扩展问题 {
    /*
    https://www.nowcoder.com/practice/953b74ca5c4d44bb91f39ac4ddea0fee?tpId=230&tqId=39750&ru=/exam/oj
    dp问题, 需要找找规律
     */
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] dp = new int[n + 1];
        dp[1] = 1;
        for(int i = 2;i <= n;i++){
            for(int j = i - 1; j >= 1;j--){
                dp[i] += dp[j];
            }
            dp[i] += 1;
        }
        System.out.println(dp[n]);
    }
}
